An old curse supposedly goes, “May you live in interesting times.” Pretty obviously this curse, or one of its close cousins, has been hurled at us inhabitants of the 21st century, for this century bids fair to be the most interesting ever.

Everything will change. The way we live on this planet, including the way we house ourselves, eat, work, learn, get from one place to another, communicate and use currency. The way we conceive of ourselves and our place in the world, including the ways we think of religion, morality, justice, our histories and cultures and the way we define what matters. With nearly seven billion of us here at the beginning of the century, we will be changing the way we think about reproduction, and perhaps even the way it is accomplished. And all of these changes will be, and are being, reflected in our art and music.

One of the largest changes will come to science. Since at least the time of the pre-Socratic philosophers, thinkers and researchers have dreamt of and searched for a single principle to explain the world. This search for a grand, unifying theory continued up through Descartes and then Newton — who gave the search, in physics, a large and much-needed dose of steroids. After the individual sciences started to mature at their own pace, developing their own theories and methodologies, the search for a unifying theory became, and remains today, the search for unifying theories — each science searching for its own.

In the 21st century, we will see this search move in two opposing directions. Some sciences will move closer to their dream of a unifying theory; others will see their dream dashed to bits. Why these two directions should prevail is itself a matter of great interest. To be specific, let us consider two sciences: biology and cognitive science.

Biology’s success at finding a unifying theory is one of the great success stories in the history of science. The discovery of evolution and the creation of the theory of evolution was a remarkable accomplishment. To this day, however, many don’t appreciate how powerful the theory of evolution is. This will change.

The way we humans define ourselves is deeply tied up with our religions and our moralities. As this century progresses, the theory of evolution will extend its reach to cover both of these. Evolutionary theory is now beginning to explain why humans are religious, why religions are structured the way that they are, and even why religions have a supernatural component. Evolution is also being used to explain our moralities — the implicit, internal rules of conduct that knit together our societies and are the foundation of our cultures. Furthermore, evolution is linking our embrace of religion and the way we conceive of our morality and moral duties. Allies in this bold advance include neuroscience, psychology and philosophy. It is possible that by the end of the century we will know the biological and neuropsychological reasons that humans are religious and why we parse the world of human actions into right and wrong, good and bad, in the ways that we do. This possibility is sobering, to say the least, but there could well be important benefits from such advances.

The 21st century is likely to continue to be a century tortured by terrorism of various sorts. The sheer stress of population increase will be one major contributor to this. But much of the terrorism will be, as it now is, based on deep religious and cultural differences. It’s a reasonable hope that we could place these differences in a better perspective once we know their biological and psychological origins. This might allow us to mitigate the problem of terrorism, for often progress toward solving a problem is made by knowing its cause.